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Old 1st February 2013, 01:27 PM   #33991
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Quote:
Originally Posted by RNMarsh View Post
Motorized pot -->- motorized rotary switch for shunt type atten.?
Yes, why not.
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Old 1st February 2013, 02:05 PM   #33992
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Default Motorized rotary switch - follow up.

Another NON-SHORTING deck added to that quadruple switch could be used for positioning, if needed.
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Old 1st February 2013, 02:55 PM   #33993
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Quote:
Originally Posted by BV View Post
It has nothing to do with that..The only reason is sound quality (minimal degradation). And differencies between PGA, DAC with OA in multiplying mode and relay attenuator are clearly audible and measurable, even with "ordinary" speakers.
Everything is clearly audible. there is a difference between any DAC, any power amp etc.
The question is: did-it change the sound in a bad way, "which can reduce your listening pleasure" as for a good potentiometer, my response is 'NOT really'. And LESS than a good potentiometer.
Does-it reduce separation between instruments ? No.
Does-it change the texture of them ? No (Pots add a little granular sound)
Does it reduce instant dynamic (transients) ? Not sure.
Did-you lose details or presence ? Not sure.
Does it add noise you can notice ? No.
Are the levels steps low enough for comfort ? yes.
Are tuning the volume agreeable enough ? Yes.

The changes that occurs are less than those that could happen if the mix of the record you listen too began half an how later. or mastered in an other place.
Of course, you'll be sure the circuit is correctly implemented, source is low impedance, grounds well separated between digital and analog, PSU low noise enough and good decoupling of the PGA analog. And no capacitances in the signal path.
Here is the sens of my 'snobbish'. there is a limit of the quest of 'absolute', because 'absolute does not exist.
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Old 1st February 2013, 03:34 PM   #33994
BV is offline BV  Slovakia
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Perhaps you could point out where the measurements show the use of a multiplying DAC?
Look attached pictures, DAC+OA measurement is about 3 years old, loopback ,unbalanced connection (so visible 50Hz), PGA in balanced connection. Same level, same measurement conditions.
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Old 1st February 2013, 03:37 PM   #33995
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What Parasound has been using for many years is a motorized Alps pot, sometimes 4 gang, for a volume control. Personally, while I have never MEASURED any problem with Alps pots, I prefer TKD, P&G, or a quality dual selected 10 turn wirewound resistor, for a volume control. Unfortunately, TKD is seemingly impossible to work with, especially motorized, although I once had a sample that worked great.
P&G is rated to only 10K, (in my experience) too low for Parasound, and while they are expensive, I suspect that the really well tracking ones are 'cherry picked' out for major manufacturers, like Levinson and Krell, in advance.
10 turn wirewound pots are VERY EXPENSIVE, almost too much for CONSTELLATION, and that is saying something.
However Alps, is greatly reducing its selection, and we may have to use an electronic volume control in future designs, because of this.
Personally, anybody who prefers a deliberately reduced bandwidth is not someone who I would rely on for subjective input, so that leaves a few inputs here in suspension.
Now, what about REAL BANDWIDTH? Normally the loudspeaker will be the ultimate limit, and reducing the bandwidth in the electronics should barely make a difference, UNLESS the playback is passing nearly ultrasonic garbage to the following amps and making them misbehave.
I don't know specifically why most tweeters have a problem passing info above 20KHz, but it appears to be so, including most horns.
Therefore the RATE OF CHANGE of the drop-off of the high frequencies must be an important contributor to the SOUND of the high frequency attenuation, more than just extended response of the electronics.
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Old 1st February 2013, 03:43 PM   #33996
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by BV View Post
Look attached pictures, DAC+OA measurement is about 3 years old, loopback ,unbalanced connection (so visible 50Hz), PGA in balanced connection. Same level, same measurement conditions.
Can show the circuits you used. A lot of this has to do with implementation.

That is NOT the PGA23xx I know and love! 2H -75 dB down? You should be sitting between -100 and 110 dB into a 2k load.

Thanks
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Old 1st February 2013, 03:50 PM   #33997
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Quote:
Originally Posted by BV View Post
Look attached pictures, DAC+OA measurement is about 3 years old, loopback ,unbalanced connection (so visible 50Hz), PGA in balanced connection. Same level, same measurement conditions.
OK, so it's not MDACs in general, it's either the specific one you used or your implementation. The measurements on the ML I linked to were outstandingly good.
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Old 1st February 2013, 03:56 PM   #33998
BV is offline BV  Slovakia
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Recomended circuits, no faulty implementations .. Be sure, there was no problem. The only difference was in a part of PCB around volume regulation. Measurements on whole preamp.
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Old 1st February 2013, 03:59 PM   #33999
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Quote:
Originally Posted by BV View Post
...no faulty implementations
Well, since others got much better results using the same technology, then clearly the implementation WAS faulty or you chose a poor part and are trying to generalize from a single bad example.
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Old 1st February 2013, 04:00 PM   #34000
BV is offline BV  Slovakia
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The measurements on the ML I linked
Where? Please link. DAC8043 was used in ML383. DAC is a way better than PGA..
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